1. Field of the Invention
The present invention relates generally to the field of steering and navigation systems for watercraft, and particularly for pleasure craft. Even more particularly, the invention relates to a technique which employs dual electric motor stem drives in conjunction with a forward thruster for a range of navigational controls.
2. Description of the Related Art
Various systems and configurations have been proposed and are currently in use for navigating watercraft. Depending upon the size and use of the watercraft, these systems include both internal combustion-driven propulsion units, and electric motor drives. In the former case, outboard motors may be mounted to a transom of a boat, and used alone or in tandem to produce the desired thrust for navigating the boat for its intended use. Similarly, inboard motors typically include an internal combustion engine housed within a compartment of the hull, with a driven propeller extending through the hull to propel the boat in a similar manner.
Electric motor drives for watercraft have been developed, and are particularly well suited to slow-speed and special purpose applications. For example, trolling motors and electric outboards are available for slow-speed navigation, and are well suited to fishing boats, wherein quiet operation is essential. Indeed, electric motor drives are the favored solution for such activities, and are typically used in tandem with outboard or inboard motor systems to provide flexibility and to enhance the utility of the craft for a wide range of activities.
While propulsion systems of the type described above are generally suitable for many uses, they are not without drawbacks. For example, internal combustion engine-driven systems are simply unsuitable for applications in which low noise levels, low emission levels, and low speed navigation are important. Similarly, conventional electric propulsion systems often do not provide a desired degree of navigational flexibility, and suffer from a tendency to become entangled in weeds or other plants growth, to contact submerged objects and obstructions, and so forth. Moreover, conventional trolling motor systems typically require that a drive unit and directional unit be rigidly mounted to a deck surface, both during deployment and when stowed. Consequently, a second of the deck becomes essentially unusable and is severely obstructed. These systems also detract from the aesthetic appeal of the watercraft, and may provide an unacceptable level of aerodynamic drag, both when deployed and when stowed.
There is a need, therefore, for an improved propulsion and navigation system for watercraft, particularly for pleasure craft. There is, at present, a particular need for a system which would eliminate or reduce the need for deck encumbrances, while providing effective low-speed navigation and steering. Furthermore, there is a need for a system which can be retrofitted to existing boat designs, as well as incorporated into new designs, controlled through relatively intuitive control devices, and provide as user-friendly a navigation system as possible.
The invention provides a navigation system for a watercraft designed to respond to these needs. The system may be retrofitted to existing boat designs, but is particularly well suited to new designs which specifically incorporate its features integrally with other hull and control elements. The technique makes use of a series of propulsion units which operate in cooperation. In particular, a pair of electric motor propulsion systems are provided in the stern region of the watercraft and may be driven at various speeds and directions to produce resultant thrust components for navigating the craft. A forward thruster unit compliments the rear propulsion units to produce thrust components which are at least partially transverse to a longitudinal centerline of the craft. That is, the forward thruster unit enables the craft to be navigated in lateral directions, either through turns (i.e. rotation of the hull) or through xe2x80x9cslidingxe2x80x9d type movement (i.e. lateral movement without rotation of the hull).
The resulting system and controls enable a wide range of navigational commands. For example, the system may be employed for relatively slow-speed navigation during activities such as fishing. In this type of operation, the technique allows for replacement or reduced dependency on conventional trolling motor or electric outboard systems. Moreover, the technique facilitates navigation into tight areas, such as between trees, stumps, and similar obstacles in a manner heretofore unavailable through conventional propulsion systems. Similarly, the technique allows for simplified docking by providing a high degree of low-speed navigability.